1. rotary total heat exchanger

The surface of the rotary heat exchanger is honeycomb-shaped and coated with a layer of adsorption material as a desiccant. Place the runner between the air ducts and divide it into two parts. The air-conditioned room is exhausted from one side, and the outdoor air enters from the other side in the opposite direction. In order to increase the heat exchange area, the runner rotates slowly (10~ 12 rpm). Half of the wheel absorbs and stores heat from hot air. When it rotates to the other side, it releases heat to transfer heat. The desiccant attached to the surface condenses the moisture in the high humidity airflow, and then it is absorbed by the desiccant. When it rotates to the other side, it releases moisture into the airflow with low humidity and transfers latent heat.

Baffles are arranged on both sides of the rotating body of the heat exchanger, so that fresh air and exhaust air flow in the opposite direction. The runner chip is made of special paper or aluminum foil, and its surface is coated with moisture absorption coating, forming a carrier for heat and moisture exchange. It rotates at the speed of 10- 12r/min, and the cold heat in the exhaust gas is first collected in the heat accumulator (flow channel core) and then transferred to the fresh air. Air passes through the heat accumulator at a flow rate of 2.5-3.5m/s, depending on fresh air and exhaust air. Therefore, both sensible heat and latent heat can be recovered.

1) Function and application scope of runner heat exchanger

Application scope of work and energy

It has excellent hygroscopicity, can recover sensible heat and latent heat, and the efficiency can reach 70% (the wheel body is covered with hygroscopic coating). Air conditioning systems with humidity requirements, such as textile mills, paper mills and some production workshops.

There is no hygroscopicity requirement. When the sensible heat is mainly recovered, the sensible heat recovery device should be adopted with no coating on the surface. When the exhaust temperature is lower than the dew point, it can absorb moisture and recover latent heat. Gymnasium, department store, industrial ventilation system

2) Main advantages and disadvantages of rotary heat exchanger:

merits and demerits

1. sensible heat and latent heat can be recovered 1. Large equipment, occupying a lot of building area and space.

2. There is a certain self purification in the process of reverse alternation of exhaust air and fresh air. 2. The nozzle position is fixed and the pipeline flexibility is poor.

3. Different indoor and outdoor air parameters can be adapted by speed control. It has transmission equipment and needs to consume electricity by itself.

4. The recovery efficiency is high, which can reach 70-80%. 4. The pressure loss is large and it is easy to get dirty and blocked.

5. It can be applied to the exhaust system with high temperature. 5. There is leakage, and cross-contamination cannot be completely avoided.

3) Factors affecting the efficiency of runner heat exchanger:

A. airflow speed: when airflow passes through the runner, the greater the windward speed, the lower the efficiency; Otherwise, the efficiency is high, and the recommended wind speed is 2 ~ 4m/s. ..

B air filters need to be installed at the air inlets on both sides of the runner.

C. During design, it is necessary to calculate and check whether frost and ice will appear on the runner; If necessary, an air preheater should be installed on the fresh air pipeline, or an automatic temperature control device should be installed behind the heat recovery device. When the temperature reaches freezing point, it will send a signal to close the fresh air valve or open the preheater.

D. Because the total heat exchanger runner needs power, the resistance is increased, and the transmission power and investment are increased. Therefore, the recovery effect must be calculated, and the recovery effect can only be selected if the total energy consumption is significantly saved.

E it is suitable for places where the exhaust gas does not contain harmful or toxic substances.

2. Low temperature heat pipe heat exchanger

1942, American engineers put forward the principle of heat pipe. Research and trial production began in the early 1960s, and it was first used in spacecraft and nuclear reactors. In 1970s, as a brand-new heat recovery device in air system, heat pipe heat exchanger finally showed outstanding advantages in HVAC industry. Heat pipe is a heat transfer element that realizes heat transfer through the phase change of liquid itself. It has the following characteristics: (1) Each heat pipe is permanently sealed, there is no extra energy loss in the heat transfer process, there are no moving parts, and the operation reliability is high. ⑵ The structure of heat pipe heat exchanger determines that it is a typical countercurrent heat exchange, and the heat pipe runs almost isothermally, so the heat pipe heat exchanger has high efficiency. (3) Due to the heat exchange between hot and cold gases, it is easy to expand the heating area of the outer surface of the heat pipe. (4) Cold and hot gases are separated by partitions, so there is no leakage, so there is no cross-contamination problem. 5] Because the fluid channel is spacious, the resistance loss is small. [6] Each heat pipe is completely independent and easy to maintain. (7) From the comprehensive indicators of environmental adaptability, waste heat recovery efficiency, pressure loss, anti-clogging, cleaning and service life, the heat pipe heat exchanger is dominant.

Working principle: The heat pipe consists of shell, wick and end cover. The evacuated pipeline is filled with appropriate working fluid and then sealed at both ends. The heat pipe is both an evaporator and a condenser. One end of the heat flow is the evaporation section, the working medium evaporates after absorbing heat, flows to the other end, namely the condensation section for exothermic liquefaction, and flows back to the evaporation section under the action of capillary force to automatically complete the cycle.

The heat pipe heat exchanger is assembled by a single heat pipe, and the evaporation section and the condensation section are separated by a partition. The heat pipe heat exchanger completes heat transfer through the phase change of working fluid in the heat pipe. Each heat pipe is an unpowered refrigeration cycle system, and its heat transfer speed is several thousand times to ten thousand times that of the same metal. A temperature difference of 0. 1℃ will have a thermal response. Originally used in satellites to solve the problem of uneven heating on the sunny side and the shady side, it is one of the necessary equipment on satellites. Now, it is more and more widely used in air conditioning and waste heat recovery. An expert from Waseda University in Japan said: "Japan pays special attention to energy conservation and environmental protection, and heat pipe technology has found a new way for energy conservation and environmental protection because of its efficient heat transfer." Introduction and selection of heat pipe heat exchanger in HVAC design manual.

1) Main advantages and disadvantages of low-temperature heat pipe heat exchanger;

merits and demerits

1. has a compact structure and a large heat transfer area per unit volume, which is 1. Only sensible heat can be recovered, not latent heat.

2. No rotating parts, no extra energy consumption. 2. Fixed nozzle position, the pipeline lacks flexibility.

3. Each heat pipe has its own heat exchange system, which is not suitable for dirty plugging and easy to replace.

4. The heat transfer of the heat pipe is reversible, and the hot and cold fluids can be changed.

5. When the temperature difference between hot and cold air is small, a certain recovery efficiency can be obtained.

6. The temperature drop is very small, close to isothermal operation, and the heat exchange efficiency is high, 60~70%.

7. Long service life, exceeding 12 years.

2) Design considerations:

A. The low-temperature heat pipe is suitable for the temperature of -40℃~80℃ and can be used all year round. When it returns to cold, the angle is opposite to that of heat.

B the head-on wind speed should be1.5 ~ 3.5m/s.

C the partition between the cold end and the hot end adopts double-layer structure, which can prevent cross-contamination caused by air leakage.

Heat exchangers can be installed vertically or horizontally, and several can be connected in parallel or in series.

E. When the moisture content of airflow is high, (latent heat can be recovered at this time, which can be used as surplus).

F. condensate drain device shall be designed.

G. When starting the heat exchanger, the cold and hot air flows at the same time, or the cold air flows first. When stopping, the cold and hot airflow should be stopped at the same time, or the hot airflow should be stopped first.

The conclusion of Liaoning Energy Demonstration Meeting on heat pipe heat exchanger is: "This device is a secondary heating device. In the first stage, KLS series low-temperature heat pipe heat exchanger is used to recover waste heat and preheat fresh air. The second stage adopts SRZ air heater commonly used in ventilation engineering, and the two stages are connected in series, with novel structure and practical engineering. It is a new energy-saving air supply and heating unit integrating central heating and ventilation. The exhaust waste heat recovery device used in this product is KLS heat pipe heat exchanger. The heat pipe heat exchanger has passed the appraisal of National Machinery Committee and Beijing Science and Technology Commission. It is considered that the product has compact structure, stable performance and convenient operation and maintenance. More than 300 sets of this product have been produced, and the users have responded well, so the core equipment of this unit is reliable. This product has remarkable energy-saving effect, and can recover 60% of waste heat, and the investment payback period is 1-2 years. At the same time, it can also reduce environmental pollution. Experts attending the meeting agreed that this product should be actively promoted and used in enterprises in our province, and accumulated experience in the process of use, continuous improvement and perfection, which is conducive to the development of energy-saving work in our province. "

Second, the low temperature heat pipe heat exchanger energy saving and economic benefit analysis:

According to the outdoor temperature of Shenyang in winter-19℃ and indoor temperature of 20℃, the exhaust air volume is 30 000 m3/h, and the energy loss is 370 000 Kal/h, which is equivalent to the heat generated by a 0.7-ton boiler per hour. According to the calculation of 60% efficiency, the heat that can be recovered by the heat pipe heat exchanger per hour is 222,000 kal/h.

1. Working principle of plate heat exchanger;

Assemble the passage formed by the interval between upper and lower floors with special paper material or aluminum foil. Intake air passes through odd layers, exhaust air passes through even layers, and heat is transferred through the contact between air and laminates. The efficiency of air supply and exhaust is the highest when it is in countercurrent, but the material is the most stressed when it is in countercurrent movement, and it is easy to blow through the heat exchanger. Therefore, cross-flow structures are usually adopted, and when they are used for full heating, the surface should be coated with moisture-absorbing materials.

Advantages and disadvantages of plate heat exchanger:

merits and demerits

1. Simple structure and safe operation 1. The equipment is large and needs to occupy more building space.

2. No transmission equipment, no power consumption. 2. It is easy to get dirty and blocked, difficult to clean, and has great resistance.

3. No intermediate heating medium is needed. 3. When the air volume is large, the choice is limited.

4. Low equipment cost

Attention should be paid to the design and selection of plate heat exchanger:

First, it is only applicable to general air conditioning projects, and it is not applicable when the exhaust air contains harmful components.

Two. Because of the large resistance loss, in order to use fresh air and reduce energy consumption in the transitional season, a bypass duct should be designed next to the heat exchanger to let fresh air pass through.

Three. Air pipes and bypass ventilation pipes connected to the heat exchanger must be equipped with air valves with good air tightness.

Ⅳ. The installation position should be convenient for replacing the iron core.